Such gas sensors are used typically for determining the concentrations of explosive gases or gas mixtures in an environment and are based, in general, on measurements with so-called heat evolution sensors or on infrared optical absorption measurements with a radiation source and with at least one measuring detector. A prior-art infrared sensor with a measuring section outside the sensor housing, in the environment containing the gas to be measured, appears from DE 197 13 928 C1.
Explosion-proof gas sensors are subject to the requirements of explosion protection, and a pressure-proof encapsulation of the housing may be additionally necessary. The optical and electronic components necessary for the measurement, i.e., the measuring module, which may lead to ignition of a combustible gas without special protection, are accommodated in a special housing, which meets the requirements imposed on the particular type of protection required.
The interface to the environment is via at least one duct of a pressure-proof design for the electrical cable leads.
Outside the housing encapsulated in a pressure-proof manner, the measuring space is in an environment that is accessible to the gas to be measured, which may possibly be explosive, i.e., the measured gas sample holder.
Based on the requirements for approval concerning explosion protection, the cable ducts are of a very complicated design and therefore cost-intensive. In addition to this are the extensive and likewise cost-intensive tests associated with the approval.